Should you drink coffee before workouts? It may depend on your genes.

Most of you runners and triathletes probably know that caffeine is widely accepted as a performance enhancer. Though the jury is still out on the exact mechanism, it is believed that caffeine functions in several ways related to endurance performance. It likely has a role reducing perception of fatigue by impacting certain receptors in the brain, and it may also influence neuromuscular function in skeletal muscle and improve fuel utilization of fats.

The amount of caffeine that can improve endurance performance is in the range of 3 to 6 mg per kilogram of body weight, consumed on hour before exercise. That’s about 1-3 cups of coffee before workouts.

But what if the impact of the caffeine on performance was affected by your genetics?!

This is a new area of thought, and though not well researched yet, I wanted to give you a little breakdown today. {Before I start, let me tell ya that I am not a genetics expert, so apologies if I’m botching this terminology at all.}

Scientists know that differences in our genetic makeup affect how we metabolize caffeine. There are several genes involved, but the main one we look at is called the CYP1A2 gene. This gene is responsible for directing production of an enzyme in the liver that breaks down caffeine.

There are several variations in the CYP1A2 gene that can affect caffeine metabolism. None of them are particularly well studied when it comes to performance, but probably the most well studied is the rs762551 single nucleotide polymorphism (SNP). The genetic makeup here can be one of three types, made up of a combination of two different alleles (A and C). “A” is associated with faster caffeine metabolism while “C” is associated with slow metabolism. That means you can have one of the following combinations:

AA – fast metabolizer

AC – slow metabolizer

CC – slowest metabolizer

I was able to find three studies on this particular genetic variation:

1. A 2016 study on 3km cycling performance among recreational cyclists looked at the effect of caffeine ingestion and as well as caffeine mouth rinsing on performance, among an AA vs an AC genotype. Ingesting caffeine before exercise plus the caffeine mouth rinse had a benefit on performance in both types. But when they looked at only caffeine beforehand (no mouth rinse during), that was only beneficial in the AC type.

2. Another cycling study looked at two 40km time trials among trained male cyclists. Participants were categorized into two groups: AA genotype vs. C allele carriers. Ingesting caffeine an hour before the time trial resulted in better performance in both groups, but this was more pronounced in the AA group.

3. A third cycling study broke down recreational athletes in a similar way – AA genotype vs. C allele carrier. In this study, caffeine did not impact performance, and there were no differences between genotypes.

So interestingly, here we have three studies with three different results when looking at caffeine before exercise: one that showed better performance with the C allele, one that showed better performance without it, and one that showed no difference.

But there were some major differences between these studies – for example, the second study looked at trained athletes while the first and third looked at recreational cyclists. The first study was a sprint (3km), while the second was a measure of endurance performance (40km). I’m tempted to veer towards the second study since it’s specific to endurance athletes, which suggests that fast metabolizers would have the upper edge with caffeine intake, but of course we need more research about this.

What prompted my interest in researching this was a session at FNCE last October that looked at another CYP1A2 gene variation – a single nucleotide polymorphism (rs2069514) that can be broken down by these combinations:

GG – fast metabolizer

GA – slow metabolizer

AA – slowest metabolizer

In this session, RD and PhD candidate Nanci Guest shared her recent research on the GG vs. GA/AA metabolizers. This study hasn’t been peer reviewed yet, so it’s worth taking with a grain of salt. But in her research, the GG fast metabolizers had a boost in 10km cycling time trial performance with caffeine ingestion beforehand. Those with the GA breakdown had insignificant changes. Those with the AA slowest metabolizer genetic makeup actually slowed down with caffeine use.

Super interesting, right?! Who knew that coffee before workouts could be so complex?!

Obviously no firm conclusions can be drawn about this yet, but keep an eye out in the next few years for more research on this as well as other areas of nutrigenomics. I think we’ll be seeing a true testament to the fact that sports nutrition can really be an individualized science.

In the meantime, pay attention to the impact of caffeine on your body. If you feel like green tea or coffee before workouts is not helping you or causing jitters and rapid heart rate, don’t feel like you need to use it in the name of performance. Because depending on your genetics, it could actually be causing you to slow down.

Share with me: Do you use caffeine before races or drink coffee before workouts? Have you ever heard about the different types of caffeine metabolizers?

Chrissy Carroll is a Registered Dietitian and USAT Level I Triathlon Coach. She specializes in sharing nutrition and fitness tips, as well as recipes, for runners, triathletes, and active women.Chrissy holds a Bachelor's Degree in Nutrition, a Masters Degree in Public Health, and is also an ACSM Certified Personal Trainer.

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I’m a fellow nutritional scientist, and I’m loving the scientific breakdown! We need more REAL science in the blogging space. I’m excited to see what kind of research comes out of this in the future. It’s truly amazing how much we don’t know about nutrition and our bodies.

Huh. I’m glad there’s a genetic component to whether caffeine is beneficial. There’s such a wide gulf of anecdotal evidence that it makes sense genetics plays a role. Of course, I bet there’s a significant placebo effect for most of us if we think we’ve ingested caffeine.

I’m curious where I fall. I’ve given up caffeinated coffee except for pre-race. Recently, I did a 14-mile training run, and I allowed myself cup of coffee prior to that workout. (I was at church. Coffee Hour is a lesser sacrament for Episcopalians.) In those instances, I find I don’t have trouble sleeping that night. My guess is the caffeine is metabolized by the workout. But given that I’ve found that even a cup of regular coffee can prevent me from sleeping for twenty hours or so, I’m chary about the stuff. Nothing wrecks training and recovery like trying to function on three hours of sleep.

I feel like you’re sticking to it the right way – use it before races but veer away from it on an everyday basis if it affects sleep. I wonder if the adrenaline component of the race affects the metabolism aspect (no clue, but off to research it now, haha!).

This is indeed a very interesting read. I have never thought of anything like this before.. When I get up in the morning, before starting my 5k run, I make sure to drink coffee first. It’s just so hard for me without drinking coffee in the morning, and I’ve never thought that drinking coffee may have an effect on me…I’ll pay more attention the next time.. Do you have any tips before starting a run? I’m just an occasional runner, whenever I have the free time, specially in the morning.

Very interesting article you have here! Thanks for sharing it with us. I love the fact that you actually incorporated studies and research in your post. It’s very informative. I love coffee and to think that there are studies made about coffee relating to genes. By the way, where do you think you fall from those categories?